In an exhaust gas cleaning apparatus of an exhaust gas recirculation (EGR) type, an EGR valve device, which is opened for recirculating a part of the exhaust gas from the exhaust manifold to the intake manifold in accordance with a vacuum signal from an engine port, is used. The EGR valve has a diaphragm mechanism having a diaphragm to form at least one chamber which is connected to an engine port, and has a valve member connected to said diaphragm via a rod to open the valve against a force caused by a spring acting on the diaphragm, when a vacuum signal of a predetermined level is transmitted from the port to the chamber.
The vacuum level at which the EGR valve is opened for EGR operation should be kept at a predetermined constant level for an ideal EGR operation, when mounting the EGR valve to the engine during the manufacturing of the automobile. The vacuum level at which the EGR valve is opened is determined by various dimensions, in the direction of the rod, of many parts forming the EGR valve. In the prior art, therefore, to obtain an EGR valve which opened at a predetermined constant vacuum level, it was necessary to construct many of these parts requiring accurate dimensions in the direction of the rod. Therefore, production of this EGR valve device was not only costly but caused much tiresome labour.
To avoid to making many parts having accurate dimensions, it has already been provided such an EGR valve having a screw mechanism for allowing adjustment of a position of the diaphragm with respect to the rod for opening at a predetermined constant vacuum level. However, this type of an EGR valve has a complicated construction due to the screw mechanism, thereby causing prolonged labour during assembling and results in the costly production of the EGR valve.